class Solution {
public:
    bool lemonadeChange(vector<int>& bills)
    {
        int five = 0, ten = 0;
        for (auto x : bills)
        {
            if (x == 5)
                five++;
            else if (x == 10)
            {
                if (five == 0)
                    return false;
                five--; ten++;
            }
            else
            {
                if (five && ten)
                {
                    ten--; five--;
                }
                else if (five >= 3)
                {
                    five -= 3;
                }
                else
                    return false;
            }
        }
        return true;
    }
};